From: Clem Dickey <dickeycl@us.ibm.com>
To: pgsql-sql@postgresql.org
Subject: "<query expression body> ::= <joined table>" grammar rule not accepted by Postgres
Date: Wed, 15 Jun 2011 14:50:09 -0700
Message-ID: <OF650DD52B.2DDBF653-ON852578B0.00699C93-882578B0.0077F2AD@us.ibm.com> (raw)
This expression is (I think) a well-formed query, but is rejected by
Postgresql 8.4 (t is a table name).
t t1 NATURAL JOIN t t2;
Here is the relevant parts of grammar (with some optional elements omitted
for simplicity):
<query expression> ::= <query expression body>
<query expression body> ::= <joined table>
<joined table> ::= <natural join>
<natural join> ::= <table reference> NATURAL JOIN <table primary>
<table reference> ::= <table primary>
<table primary> ::= <table or query name> [ <correlation name> ]
<table or query name> ::= <table name>
Nor is this use of <joined table> accepted in the <query expression> form
of a <with list element>:
WITH tw AS ( t t1 NATURAL JOIN t t2 ) TABLE tw;
This leads me to believe that the unrecognized grammar rule (in SQL99
standard terms) is
<query expression body> ::= <joined table>
There are, of course, other ways to express the operation, including
SELECT * FROM (t t1 NATURAL JOIN t t2);
But I am curious why the first expression is not accepted, besides the
immediately obvious "it's not in the Postgres version of the SQL grammar."
Clem Dickey
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To: pgsql-sql@postgresql.org
Cc: dickeycl@us.ibm.com
Subject: Re: "<query expression body> ::= <joined table>" grammar rule not accepted by Postgres
In-Reply-To: <OF650DD52B.2DDBF653-ON852578B0.00699C93-882578B0.0077F2AD@us.ibm.com>
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